Process for removing nitrogenous compounds from hydrocarbon oils



Patented Feb 14, 1961 United States Patent" Office 2,971,906 rnocrss For: mnrovmo NITROGENOUS courrouNns mom rrvnnocanson ons Alfred lemley wem waua m. a ShellllCompmy,aeorpontlnlofDelaware 'Nsnmm mumrnrssqsmudsusss Clai-spelorlty,applicaflcnGreatIrltainAIg.25,1955

'IClai-s. cues-254 This invention relates to a process of refining hydrocarbon oils containing nitrogen-base compounds with phosphoric acid and the recovery and reuse of the acid in the process. I

Many crude petroleum oils contain small amounts of various nitrogenous compounds. These have been identilied in part as certain pyridines, e.g. 3- and 4-cyclopentylpyridine and 2,4-dimethyl-6-(2,2,6-trimethylcyclohexyl)- pyridine, and quinolines, e.g., 2,3,8- and 2,4,8-trimethylquinoline and 2,4-dimethyl-8isobutylquinoline. These nitrogenous compounds have potentially great value as' chemical and dye intermediates. However, when present in various hydrocarbon oil fractions, such as mineral lubricating oils, fuel oils, diesel oils, and gasolines, they may cause deposit or lacquer formation in the systems in which the oils are used. Thus, small traces of nitrogenous compounds in mineral lubricating oils may cause lacquer formation on the walls of the cylinders of diesel engines in which such oils are used, and in gasolines may cause fouling in the inlet manifold systems of internal combustion engines.

Nitrogenous compound are removed to a varying extent in conventional refining processes, such as distillation, solvent extraction, and acid and clay treating. The usual method of removing nitrogenous compounds from hydrocarbon oils in a separate operation is extraction with sulfuric acid in the liquid phase. However, when using this process specifically for removing nitrogenous compounds (as distinct from using it to achieve some other end and only incidentally removing any mtrogenous compounds which may be present) there are certain disadvantages. Thus, sulfuric acid may extract and/ or oxidize valuable components other than the nitrogenous compounds and may partially oxidize nitrogen compounds, the spent sulfuric acid is diflicult to recover and it is diflicult to recover the nitrogenous compounds from the spent sulfuric acid.

As an acid phosphoric acid is also available to remove basic nitrogenous substances. It gives an advantage of not oxidizing and degrading the nitrogen compounds. However, phosphoric acidis well known to be a much weaker acid than sulfuric acid and it is usually the desire to remove even the weakest basic nitrogenous substances so that the usual practice is to use sulfuric acid.

The nitrogenous material is usually recoverd from the acid extract by neutralin'ng the acid with an alkali, such as sodium hydroxide, to spring the nitrogen bases. This, however, has the disadvantage of converting the acid to salt, so that it is not economically feasible to recover the acid for reuse.

It is a principal object of this invention to provide an improved process for the removal of nitrogenous compounds from hydrocarbon oils. A further object is to provide such a process wherein the nitrogenous compounds are recoverable without appreciable change in chemical nature. Another object is to provide such a process in which the extracting agent for removing the nitrogenous compounds is readily recovered from the extractinaformsuitableforremeintheproceas. These objects will be better understood and others will appear from the description of the invention.

It has now been found that hydrocarbon oils may be treated with phosphoric acid to obtain an extract containing the nitrogenous impurities and the phosphoric acid in the extract recovered in a form suitable for reuse as an extracting agent. The said proees comprises (UhMixing the oil with phosphoric acid in the. liquid (2) Separating the oil from the spent phosphoric acid extract,

(3) Mixing the extract with water and a volatile waterimmiscible organic solvent, and, if required to ensure phase separation, 'a volatile water-miscible organic solvent,

(4) Stratifying and separating the aqueous phase containing the phosphoric acid from the water-immiscible orgamc solvent phase containing the extracted mtrogenous compounds, and

(5) Distilling the said aqueous phosphoric acid phase to remove any water-miscible organic solvent present and I a portion of the water present to produce a residual aqueous phosphoric acid of suitable strength for reuse to extract nitrogenous compounds from a further portion of hydrocarbon oil.

.It is possible to recover the nitrogenous compounds from the organic phase separated in step (4) above, for example by distilling otf the solvent. The organic solvents used, can, of course, be recovered and recycled in the process.

The hydrocarbon oils to which this invention is applicable include mineral lubricating oils, gas oils, diesel fuels,- jet fuels, gasolines and fuel oils. It is particularly applicable to mineral lubricating oils and gasolines which,

traction, the make-up acid being of such a strength as to give the desired concentration for extraction. Lower concentrations of acid can be used in the extraction, for example down to about 70% by weight, but the percentage of nitrogen compounds extracted then decreases.

In some cases, as for example, when emulsification between the aqueous phase and the water immiscible solvent phase tends to occur, the use of a relatively watermiscible solvent improves separation between the phases. The volatile water-miscible organic solvent in many cases may be a volatile water-miscible ketone, alcohol, ether or ester. Suitable solvents are methyl, ethyl, isopropyl, n-propyl or tertiary butyl alcohol, acetone, methyl ethyl ketone, methyl acetate or formate, methylal, dioxane and ethylene glycol monomethyl ether. The solvent will usually have a boiling point below 125' C. and a solubility in H O of over 300 g. per liter at 20 C. Preferably it has a boiling point below 100' C., for example between 60 C. and C.

The volatile water-immiscible solvent may be a volatile hydrocarbon such as gasoliiie, petroleum spirits, naphtha, benzene, xylene, toluene, hexane, heptane, octane, cyclohexane and methyl cyclohexane. Non-hydrocarbons, such as chloroform, carbon tetrachloride, dibutyl ether, dimethyl carbonate, and trior tetrachloroethane,mayalsobeusedandingeneralgiverisetoless 3 emulsion dimculties than the hydrocarbons. Usually the water'immiscible solvent will have a boiling point below 7 160' C. and the solubility-in 11,0 of under 25 g. per liter at 20 C. Preferably it has a boiling point below 120' C. v

The treatment of the oil with the phosphoric acid may be carried out batchwise or continuously, and in a single stage or plural stagewise. The treatment is usually carried out at a temperature between C. and 100' C., preferablybetween 40' C. and '60 C. The ratio of oil to phosphoric acid employed depends on a number of factors, such as thetype and quantity of nitrogenous compounds to be extracted, the concentration of the acid used andthe method of contacting employed. Generally a weight ratio of oil to phosphoric acid of between 100:1 and 1:1 will be employed. The duration of the acid treatment may vary considerably, for example from a few minutes to several hours.

- When the acid treatment is completed, theoil is separated from the spent acid, for example in a centrifuge or by settling and separation, and may then be freed from the last traces of acid by washing with water or alkali or by treatment with adsorbent clays, with or without a solid alkaline material, such as lime.

Recovery of the phosphoric acid from the spent acid in a form suitable for'reuse in the process presented great dificulty before discovery of the present method. Thus, the mere addition of water to the'spent acid fails to release the'extracted nitrogenous compounds and, moreover, distillation of the spent acid, even under reduced pressure, is useless because water is lost to form pyrophosphoric acid. when, however, water and a volatile waterimmiscible organic solvent, such as petroleum spirit, are added to the spent acid, the extracted nitrogenous compounds enter the water-immiscible phase, which can be separated from the aqueous phase containing the phosphoric acid. Water is added to the spent acid to dilute it and so facilitate the transfer of the nitrogenous compounds to the water-immiscible organic solvent phase. This dilution water may be added before, simultaneously with or after the addition of the solvent to the spent acid, provided the whole is well mixed before the separation of the aqueous and water-immiscible organic solven phase is carried out. Generally, suflicient water will be added to dilute the phosphoric acid in the aqueous phase to between 25 and 60%, preferably 40 and 55%, by weight H;PO To facilitate separation of the two phases in some cases, a relatively water-miscible organic solvent is added. The

separated water-immiscible phase is then preferably treated to recover both the water-immiscible solvent and the extracted nitrogenous compounds, while the aqueous phase is distilled to remove any water-miscible solvent used and suflicient water to leave a phosphoric acid of sufficient strength for reuse in the process. This distillation is preferably carried out under reduced pressure. The water-miscible solvent, if used, can be dehydrated, if necessary, before recirculation to the process, although clearly complete dehydration is not necessary.

The invention is illustrated by the following examples in which the parts referred to are parts by weight unless otherwise stated and the relationship of the parts by weight to the parts by volume is that of the kilogram to the liter.

Example I by volume of water, 60 parts by volume of isopropyl the lubricating oil.

alcohol and 100 parts by volume of petroleum spirit (boiling range C. to C.) and the "whole intimately mixed and then allowed-to settle and separated. The petroleum spirit was distilled from the separated petroleum spirit phase to leave 4 parts of a residue which consisted mainly of nitrogenous compounds.

The aqueous phase was distilled at 150 C. and under a pressure of about 20 ml. of mercury .to remove the isopropyl alcohol and some water and leave 83.5'parts of phosphoric acid (84% by weight H;PO This acid was then used in the extraction of a further quantity of 4 Example 11 400 parts of a mineral lubricating oil having a viscosity of 170 seconds Redwood I at 140 F. and a basic nitrogen content of 6 parts per million extracted with 44.4 parts of phosphoric acid (88% by weight H;PO by intimately mixing the oil and the acid for 30 minutes at room temperature. The oil and spent acid were then allowed to settle and were separated. The oil had a basic nitrogen content of 2 p.p.m.

To the separated spent acid, there were added parts by volume of water, parts by volume of acetone and 125.parts by volume of petroleum spirit (boiling,

range 60 C. to- 80 C.) and the whole intimately mixed, allowed to settle and separated. The petroleum spirit was distilled of from the separated petroleum spirit phase to leave 0.2 part of a'residue which consisted mainly of nitrogenous compounds. l

The aqueous phase was at 150' C. and under a pressure of 40 mm. mercury .to remove the acetone and some water and leave 45 parts of phosphoric acid (87% by weight H,PO This represented a 99.2% recovery of the phosphoric acid which was thenused in the extraction of a further quantity of the lubricating oil.

Example Ill 400 parts of a mineral lubricating oil having a viscosity of 170 seconds Redwood I at F. and a basic niuogen content of 6 parts per million were extracted with 42 parts of phosphoric acid' (88% by weight H,PO by intimately mixing the oil and the acid for 15 minutes at 25 C. The oil and spent acid were then allowed to settle and separated. The oil then had a basic nitrogen content of 2 p.p.m.

To the separated spent acid there were added 100 parts by volume of water and 100 parts by volume of chloroform and the whole intimately mixed, allowed to settle and separated. The chloroform was distilled'otf from the separated chloroform phase to leave 0.2 part of a residue which consisted mainly of nitrogenous compounds. The aqueous phase was distilled at C. and under a pressure of 1 to 2 mm. mercury to remove all the water and leave 36.6 parts of phosphoric acid (100% by weight H,PO This represented a 99% recovery of the phosphoric acid which was then used in the extraction of a further quantity of the lubricating oil.

Example IV A straight-rungas oil having a nitrogen. content of 50 parts per million was agitated with 10% by volume of phosphoric acid (88% by weight H,PO for 10 minutes at 25' C. The oil and spent acid were then allowed to settle and separated. The separated gas was washed with dilute caustic soda to remove the last traces of acid and was then found to have a nitrogen.

content of '30 parts per million.

To the separated spent acid, there was added an equal volume of petroleum spirit (boiling range 60' C.- to 80' C.) and an equal volume of water and the whole intimately mixed and then allowed to settle and separated. The aqueous phase was distilled at 150 C. and

under a pressure of 20 mm. mercury to removev some of the water and leave a concentrated phosphoric acid (84% by weight H PO which was used in the extraction of a further quantity of the gas oil.

It was found that this treatment of gas oil with phosphoric acid not only lowered the nitrogen content of the oil, but also lowered the insoluble gum content. Thus, the gas oil treated in this example, on heating for one hour at 150 C. had an insoluble gum content of 4.6 mg. per 100 ml. After the treatment with phosphoric acid, however, as described in the example and then heated for one hour at 150 C., the insoluble gum content was only 1 mg. per 100 ml.

I claim as my invention:

1. A process for removing nitrogen bases from hydrocarbon oils with phosphoric acid and then regenerating said spent liquid aqueous phosphoric acid treating solution containing nitrogenous compounds extracted from the nitrogen base-containing hydrocarbon oil, the steps comprising intimately mixing said spent phosphoric acid containing nitrogenous compounds with added water and a relatively water-immiscible organic solvent having a boiling point below 160 C. at atmospheric pressure and a solubility in water under 25 grams per liter at 20 C. to achieve a substantially complete transfer of the nitrogenous compounds from the phosphoric acid to the waterimmiscible organic solvent, said water being added in an amount sufficient to dilute the spent acid to a phosphoric acid concentration greater than 30 percent and not more than 60 percent by weight H PO separating the aqueous phosphoric acid phase from the organic solvent and thereafter distilling the aqueous phosphoric acid phase to remove from it such a quantity of water as to provide a regenerated phosphoric acid of snfficient strength for reuse in extraction of nitrogen bases from a further quantity of hydrocarbon oil, said distilling being carried on to provide a regenerated acid of at least 70 percent by weight H PO and reusing the regenerated acid for removing the nitrogen bases from said hydrocarbon oils containing the same.

2. The process of claim 1 wherein the phosphoric acid is initially added in the form of an aqueous solution of over 70 percent concentration to give a weight ratio of oil to acid of from 100:1 to 1:1, the added water is suflicient to dilute the acid in the aqueous phase to a concentration of from to percent by weight H PO and the aqueous phase is distilled to yield phosphoric acid of more than percent by weight H PO 3. The process of claim 1 wherein a relatively watermiscible organic solvent having a boiling point below C. at atmospheric pressure and a solubility in 11,0 of over 300 grams per liter is added to the spent acid with the water.

4. The process of claim 1 wherein the nitrogenous compounds present in the separated organic solvent phase are recovered by distilling the solvent.

5. The process of claim 1 wherein the hydrocarbon oil is a mineral lubricating oil.

6. The process of claim 1 wherein the hydrocarbon oil is a gas oil.

7. The process of claim 1 wherein the phosphoric acid used to treat the oil has a concentration of 80-90 percent by weight H PO References Cited in the file of this patent UNITED STATES PATENTS 1,914,953 Malishev June 20, 1933 1,929,442 Mulligan Oct. 10, 1933 1,968,544 Vana July 31, 1934 2,302,956 Retailliau Nov. 24, 1942 2,368,554 Lorenz Ian. 30, 1945 2,410,906 Stewart Nov. 12, 1946 2,717,230 Murry et a1. Sept. 6, 1955 

1. A PROCESS FOR REMOVING NITROGEN BASES FROM HYDROCARBON OILS WITH PHOSPHORIC ACID AND THEN REGENERATING SAID SPENT LIQUID AQUEOUS PHOSPHORIC ACID TREATING SOLUTION CONTAINING NITROGENEOUS COMPOUNDS EXTRACTED FROM THE NITROGEN BASE-CONTAINING HYDROCARBON OIL, THE STEPS COMPRISING INTIMATELY MIXING SAID SPENT PHOSPHORIC ACID CONTAINING NITROGENOUS COMPOUNDS WITH ADDED WATER AN A RELATIVELY WATER-IMMISCIBLE ORGANIC SOLVENT HAVING A BOILING POINT BELOW 160*C. AT ATMOSPHERIC PRESSURE AND A SOLUBILITY IN WATER UNDER 25 GRAMS PER LITER AT 20*C. TO ACHIEVE A SUBSTANTIALLY COMPLETE TRANSFER OF THE NITROGEOUS COMPOUNDS FROM THE PHOSPHORIC ACID TO THE WATERIMMISCIBLE ORGANIC SOLVENT, SAID WATER BEING ADDED IN AN AMOUNT SUFFICIENT TO DILUTE THE SPENT ACID TO A PHOSPHORIC ACID CONCENTRATION GREATER THAN 30 PERCENT AND NOT MORE THAN 60 PERCENT BY WEIGHT H3PO4, SEPARATING THE AQUEOUS PHOSPHORIC ACID PHASE FROM THE ORGANIC SOLVENT AND THEREAFTER DISTILLING THE AQUEOUS PHOSPHORIC ACID PHASE TO REMOVE FROM IT SUCH A QUANTITY OF WATER AS TO PROVIDE A REGENERATED PHOSPHORIC ACID OF SUFFICIENT STRENGTH FOR REUSE IN EXTRACTION OF NITROGEN BASES FROM A FURTHER QUANTITY OF HYDROCARBON OIL, SAID DISTILING BEING CARRIED ON TO PROVIDE A REGENERATED ACID OF AT LEAST 70 PERCENT BY WEIGHT H3PO4, AND REUSING THE REGENERATED ACID FOR REMOVING THE NITROGEN BASES FROM SAID HYDROCARBON OILS CONTAINING THE SAME. 